The invention relates to a multi-stage transmission.
A multi-stage transmission having at least four planetary gear stages which are disposed one behind the other along a main axis of rotation, and in each case have a sun gear, a planetary gear support and a ring gear, is already known from DE 10 2008 055 626 A1.
The object of the invention is in particular to provide a mounting design for the multi-stage transmission known from DE 10 2008 055 626 A1 and also with the kinematically related multi-stage transmission known from DE 10 2008 055 626 A1.
The invention is based on a multi-stage transmission having at least four planetary gear stages which are disposed one behind the other along a main axis of rotation, and in each case have a sun gear, a planetary gear support and a ring gear.
It is proposed that the multi-stage transmission has a bearing which supports the sun gear of the second planetary gear stage and the ring gear of the third planetary gear stage axially with respect to one another. As a result, components which exhibit low relative speeds, in particular in forward gears in which high speeds of a drive motor are reached, can be supported with respect to one another so that, in particular, losses in the bearings can be kept low. As a result an optimized mounting design, in particular with regard to consumption, can be provided so that in particular operating costs can be lowered. In this case “supported axially with respect to one another” should in particular be understood to mean that the bearing is provided in order to transmit a force acting along the main axis of rotation. “Provided” should be understood in particular to mean specially programmed, designed and/or equipped. In this context, a “main axis of rotation” should be understood in particular to mean a common axis of rotation of the planetary gear stages. The multi-stage transmission preferably includes a gear shift unit with at least one coupling element and an intermediate shaft which connects the coupling element and the sun gear of the second planetary gear stage permanently to one another in a rotationally fixed manner and forms a bearing support element on the input side for the bearing. Moreover it is advantageous if the multi-stage transmission has a support element which is permanently connected in a rotationally fixed manner to the ring gear of the third planetary gear stage and forms a bearing support element on the output side for the bearing.
Furthermore, it is proposed that the multi-stage transmission has a second bearing which supports the sun gear of the second planetary gear stage and the planetary gear support of the second planetary gear stage axially with respect to one another. As a result, the mounting design can be further optimized. Here, the multi-stage transmission preferably includes an intermediate shaft which connects the ring gear of the first planetary gear stage and the planetary gear support of the second planetary gear stage permanently to one another in a rotationally fixed manner and forms a bearing support element on the input side for the second bearing. Moreover, it is advantageous if the intermediate shaft which connects the coupling element and the sun gear of the second planetary gear stage permanently to one another in a rotationally fixed manner forms a bearing support element on the output side for the second bearing.
It is also proposed that the multi-stage transmission has a third bearing which supports the ring gear of the third planetary gear stage and the planetary gear support of the third planetary gear stage axially with respect to one another. As a result, in particular in connection with the first bearing and the second bearing, the number of bearings required can be limited to a total of eleven bearings, so that the multi-stage transmission can also be optimized with regard to the production costs. In this case, the multi-stage transmission preferably includes a further gear shift unit with at least one coupling element and a transmission output shaft which connects the planetary gear support of the third planetary gear stage and the coupling element permanently to one another in a rotationally fixed manner and forms a bearing support element on the output side for the third bearing. Moreover, it is advantageous if the support element which is permanently connected in a rotationally fixed manner to the planetary gear support forms a bearing support element on the input side for the third bearing.
Furthermore, it is proposed that at least the bearing which supports the sun gear of the second planetary gear stage and the ring gear of the third planetary gear stage axially with respect to one another is disposed inside an inscribed circle diameter of the ring gear of the second planetary gear stage and/or inside an inscribed circle diameter of the ring gear of the third planetary gear stage. As a result, in particular, bending moments can be reduced, so that a significantly more stable support can be achieved. Particularly advantageously, at least the bearing which supports the sun gear of the second planetary gear stage and the ring gear of the third planetary gear stage axially with respect to one another is disposed inside a circular path on which the planetary gear support of the second planetary gear stage carries planetary gears around the sun gear of the second planetary gear stage.
Moreover it is proposed that the first bearing, the second bearing and the third bearing are disposed axially immediately adjacent to one another. In this way axial forces which act on one of the bearings can be transmitted to the immediately adjacent bearing and are supported thereby, so that in particular bending moments which can lead to a distortion of components supported by the bearings can reduced or avoided. “Immediately adjacent” should in particular be understood to mean that the bearings are axially spaced apart from one another by a distance which is smaller than a width of the planetary gear stages disposed axially adjacent to one another. Axially adjacent bearings have an average diameter which is at least substantially the same, wherein “at least substantially the same” should be understood to mean that the average diameters differ from one another by at most 20%.
Further advantages can be seen from the following description of the figures. An exemplary embodiment of the invention is shown in the figures. The figures, the description of the figures and the claims contain numerous characteristics in combination. Expediently, the person skilled in the art will also consider the features singly and combine them to form meaningful further combinations.